Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
from collections import deque

h, w = map(int, input().split())

ans = 0
c = []

for i in range(h):
    ci = list(input())
    ans += ci.count(".")
    c.append(ci)

sy = 0
sx = 0
gy = h-1
gx = w-1

dx = [1, 0,-1, 0]
dy = [0, 1, 0,-1]

que = deque([(sy,sx)])
c[sy][sx] = 1
while bool(que):
    y, x = que.popleft()
    if y == gy and x == gx:
        break
    for i in range(4):
        yi = y + dy[i]
        xi = x + dx[i]
        if 0 <= yi < h and 0 <= xi < w and c[yi][xi] == ".":
            que.append((yi,xi))
            c[yi][xi] = c[y][x] + 1

if c[gy][gx] == ".":
    print(-1)
else:
    print(ans - c[gy][gx])